The invention relates to a pressure foot unit for a sewing machine, in particular, a pressure foot unit which is specially adapted for use with an embroidery sewing machine.
Generally in a sewing machine, the shaft (needle bar) of a sewing needle is connected to an upper shaft which is driven for rotation through a cam or the like, and the sewing needle repeats its elevating motion in synchronism with the rotation of the upper shaft. When the sewing needle is raised to be withdrawn from a fabric, the fabric tends to be lifted by being pulled by the upper thread, thereby disturbing the thread tension. In order to prevent this, it is necessary to hold the fabric in position. In particular, a sewing operation of an embroidery sewing machine takes place while moving the fabric in diverse directions, and accordingly there is a high need to suppress the movement of the fabric during the passage of the needle. For this reason, a pressure foot in the form of a plate is disposed adjacent to the sewing needle of a sewing machine. However, it is necessary to unlock the pressure foot when moving the cloth or fabric, and hence the plate serving as a pressure foot is connected with the needle bar, and repeatedly undergoes an up and down movement through a relatively increased stroke as the sewing needle is being elevated. Hence, when the rotational speed of the upper shaft is increased to accelerate the elevating motion of the sewing needle, sounds are produced by percussion or impact as the pressure foot is being elevated.
A prior art for a pressure foot mechanism of a general sewing machine can be known from U.S. Pat. No. 4,981,094 (Class 235), for example.